Method for producing an electrically ignitable primer flement



.[52] U.S.Cl

limited States Patent [72] Inventors Hans Stadler Nuernberg; Heinz Gawlick, Fuerth; Hans Umbach, Stadelin, Germany [21 Appl. No. 767,861

[22] Filed June 20, 1968 [45] Patented Oct. 27, 1970 Dynamit-Nobcl Aktiengesellschait [73] Assignee Troisdorf, Germany [32] Priority June 4, 1965 [3 3 Germany [31] No. B47434 Original application June 6, 1966, Ser. No. 583,153, now Patent No. 3,427,972, dated Feb. 18, 1969. Divided and this application June 20, 1968, Ser. No. 767,861

[54} METHOD FOR PRODUCING AN ELECTRICALLY IGNITABLE PRIMER ELEMENT 6 Claims, 8 Drawing Figs.

Primary Examiner- Benjamin A. Borchelt Assistant Examiner-Stephen C. Bentley Attorne v(raig, Antonelli. Stewart and Hill ABSTRACT: A method for producing an electrically ignitable primer element including the steps of securing the leg portion of a U-shaped electrically conductive member to the base portion of a cartridge and severing the bridging portion of the U- shaped member to form two conductors with a gap therebetween.

fl atelnt ed Oct. 27, 1970 INVENTOR HANS STADLER HEINZ GAWLICK ,HANS UMBACH ATTORNEY.

METHOD FOR PRODUCING AN ELECTRICALILY IGNITABLE PRIMER ELEMENT This is a division of application Ser. No. 583,153, filed June 6, 1966, now U.S. Pat. No. 3,427,972, issued Feb. 18, 1969 for ELECTRICALLY IGNITED PRIMER ELEMENT AND METHOD FOR MAKING THE SAME by Hans Stadler, Heinz Gawlick and Hans Umbach.

The present invention relates to a gap-type electrically ignited primer element and the method of making the same. More particularly, the primer element includes two conductors secured within a cup-shaped carrier or bottom piece to present a gap between them, which is filled and bridged by an electrically conductive primer composition accommodated within the cup-shaped carrier; the legs of a U-shaped staplelike member may be driven through the cup-shaped carrier and the bridging portion of the U-shaped member may be severed to form the two conductors.

In the prior art primers of this type, the insulation of the metallic conductors and their attachment within the usually metallic carrier for the primer composition involve considerable difficulties.

It is an object of the present invention to eliminate these difficulties.

The present invention proposes to make the primer composition carrier from the thermoplastic material, for example, polyethylene, polycarbonate, polyamide, or polystyrene. Also, the conductors of the present invention are formed from a U- shaped staplelilte member having leg portions driven from the inside outwardly through the bottom of the primer composition cup-shaped carrier and bent to the same or opposite side. Thereafter, the bridging portion of the U-shaped member is severed to form a gap and encased in the primer composition.

The use of a thermoplastic or other insulating primer com position carrier eliminates the usual insulation problems and allows the simple inexpensive attachment of the conductors in a manner analogous to the impact driving of a staple by a gun or other machine. As in conventional stapling, the leg portions emerging from the bottom of the cup-shaped carrier are bent to one side by appropriately shaped recesses in an anvil-type backup plate supporting the bottom of the cup-shaped carrier.

The separation of the bridging portion may be accomplished by a mill or other appropriate cutting tool, or a knifelike element, which may press the separated ends into the bottom of the cup-shaped primer composition carrier to firmly anchor the conductors. It is contemplated that the gap may be in the center or outside area of the cup-shaped carrier; however, the gap must be arranged so that the igniting current will flow through the electrically conductive primer composition, which is forced into the gap after the separation, from one conductor to the other. It is contemplated that only the gap or gap area may be filled with electrically conducted primer compositions so that the majority of the primer composition may be nonconductive. To seal the primer element, the primer composition may be coated with a lacquer or other similar material. The interior of the cup-shaped member may be formed with a downwardly and outwardly extending wall portion to securely hold the primer composition within the cupshaped member. To more securely hold the primer composition, the interior of the cup-shaped carrier may be formed with a quadrangular, star-shaped, or other noncircular primer composition containing recess.

Other features, advantages and objects of the present invention will become apparent from the illustrative description of the accompanying drawing, wherein:

FIG. 1 is an axial cross-sectional view through a primer element according to the present invention, wherein the outside ends of the conductors are bent toward one side and there is a centrally arranged gap between the conductors;

FIG. 2 is a top plan view of the primer element according to FIG. 1, with the primer composition removed for purposes of illustration to show the circular shape of the primer composition recess;

FIG. 3 is a top plan view similar to FIG. 2, of another embodiment of the present invention having a quadrangular primer composition recess;

FIG. 4 is an axial cross-sectional view through another embodiment of the present invention secured in the lower portion of a cartridge case, with portions of the cartridge case omitted for purposes of illustration;

FIG. 5 is a top plan view of the primer element according to FIG. 4, showing the circular primer composition recess;

FIG. 6 is a top plan view similar to FIG. 5, of another embodiment of the present invention having a star-shaped primer composition recess;

FIG. 7 is an axial cross-sectional view of an additional embodiment of the present invention; and

FIG. 8 is an axial cross-sectional view of a further embodimerit of the primer element according to the present invention.

In the embodiment according to FIG. 1, the cup-shaped primer composition carrier or bottom piece 1 has a bottom portion 2 receiving the legs 5 and 5" of the U-shaped staplelike member, which ahs been severed at its bridging portion to form a gap 3 between the two conductors or leg portions 5' and 5". The end portions ofthe U-shaped member adjacent the gap 3 are bent over into the bottom 2 of the cup shaped carrier 1. The gap 3 is centrally located within the primer composition recess 4, which communicates with radially extending oppositely disposed slots 7 and a widened upper portion 4a; the gap 3, recess 4, slots 7, and widened upper portion 4a are filled with the electrically conductive primer composition 6. Alternatively, it is contemplated that the widened upper portion 4a may be filled with a nonconductive primer composition. The cup-shaped carrier 1 is formed with an an nular flange 8, which will abut with the rear end of the cartridge case or, additionally, the cartridge chamber wall. As shown in FIG. 2, the primer composition recess 4 is substantially cylindrical.

The embodiment of the present invention according to FIG. 3 is identical to the embodiment of FIG 1, except that the recess 4 is quadrangular to increase the adherence between the primer composition and the cup-shaped member I. Also. it is contemplated that the widened upper portion 4a in either FIG. I or FIG. 3 may have a noncircular shape.

In FIG. 4, the cup-shaped carrier has an outer recessed area 10 for receiving the bent-over ends of the conductors 5' and 5", which have been inserted in the same manner as FIG. I; the outer end of the conductors are flush with the rear-end face II of the cup-shaped carrier I. As shown in FIGS. 4 and 5, the primer composition recess 4 is frustoconical in shape to securely hold the primer composition 6 within the cup-shaped carrier ll. The forward end of the cup-shaped member 1 has an annular reinforcement 14 for snap engagement with a correspondingly shaped annular groove 15 within a cartridge case 13, which is filled with a propellant charge 12 to form a propellant cartridge for use in a bolt-setting device. for example. Also, the cup-shaped carrier 1 is provided with a flange 8 to support the cup-shaped carrier 1 against the rear-end face 16 of the cartridge case 13 and to support the cartridge within a cartridge chamber. It is contemplated that the flange could be formed on the outer end portion of the cartridge case 13. The cup-shaped member I is provided with a bottom portion 2 and slots 7, similar to the correspondingly numbered parts in FIG. I. For purposes of alignment, particularly when the outermost conductor 5" is used as the ground conductor and the innermost conductor 5 is used as the electrode contacting conductor, the flange 8 may be flattened at 17 to provide locating surfaces for aligning the conductors in a cartridge chamber.

The embodiment of FIG. 6 is identical to the embodiment of FIGS. 4 and 5, except that the recess 4 is star-shaped. As shown by the dotted lines, the recess 4 is tapered toward the forward end, in a manner similar to the recess 4 of FIG. 4.

The primer element of FIG. 7 is constructed similar to the primer element of FIG. 1, with correspondingly numbered elements. The recess 4 is constructed eccentrically with respect to the cup-shaped carrier 1 and the gap 3 formed by the conductors 5 and 5" is eccentrically located within the recess 4. The innermost ends of the conductors 5 and 5" are bent toward bottom portion 2 to form a secure attachment, but do not engage the bottom portion 2.

The embodiment of FIG. 8 is similar to the preceding embodiments with correspondingly numbered elements. The conductors and 5" are forced into the bottom portion 2, as in the previously described embodiment of FIG. 1. However, the transition portions between the bridging portion and the leg portions freely project into the primer composition 6. The outermost ends of the conductors 5' and S are bent over to project radially outwardly toward opposite sides; with this construction it may not be necessary to have a specific orientation within the cartridge chamber. in this embodiment, the recess 4 is forwardly tapered and extends to the forwardmost portion of the cup-shaped carrier 1.

it will be understood that the foregoing embodiments shown and described must be considered as examples only, and that further modifications, variations, and embodiments are intended to be covered within the spirit and scope of the present invention.

We claim:

1. The method of constructing an electrically ignited primer element, comprising the steps of: providing a generally U- shaped electrically conductive member having a bridging portion and leg portions; securing the leg portions of the U- shaped member to the bottom portion of a cartridge bottom piece to provide electrical contact portions on the outer side of the bottom piece; and severing the bridging portion of the U-shaped member to form two opposing inner conductor ends with a gap therebetween, wherein the step of securing includes forcing the leg portions outwardly through the bottom portion of the cartridge and bending the outer ends of the leg portions back toward the bottom piece.

2. The method of claim 1, wherein the steps of forcing the leg portions and bending the outer ends of the leg portions are performed simultaneously in one stapling operation.

33. The method of claim 2, including the step of bending the inner conductor ends to imbed them in the bottom portion substantially simultaneously with the severing of the bridging portion.

44 The method of claim 1, including the step of bending the inner conductor ends to embed them in the bottom portion substantially simultaneously with the severing of the bridging portion. I,

5. The method of constructing an electrically ignited primer element, comprising the steps of: providing a generally U- shaped electrically conductive member having a bridging portion and leg portions; securing the leg portions of the U- shapcd member to the bottom portion of a cartridge bottom piece to provide electrical contact portions on the outer side of the bottom piece; and severing the bridging portion of the U-shaped member to form two opposing inner conductor ends with a gap therebetween, including the step of bending the inner conductor ends to imbed them in the bottom portion substantially simultaneously with the severing of the bridging portion.

6. The method of constructing an electrically ignited primer element, comprising the steps of: providing a generally U- shaped electrically conductive member having a bridging portion and spaced-apart leg portions extending substantially laterally from the opposite ends of said bridging portion; securing the leg portions of the U-shaped member to the bottom portion of a cartridge bottom piece to provide electrical contact portions on the outer side of the bottom piece; and severing the bridging portion ofthe U-shaped member to form two opposing inner conductor ends with a gap therebetween including the step of bending the severed inner conductor ends to imbed them in the bottom portion. 

